The present invention relates generally to a bent type zoom optical system, and more particularly to a bent type zoom optical system that is reduced in terms of the whole size and thickness albeit including a reflecting surface in its optical path and having a high zoom ratio.
In recent years, imagers or imaging apparatus using an electronic imaging device as in the case of digital still cameras have been widely available. With the development and widespread use of digital still cameras, there are now growing demands for high image quality and size reductions in general, and for slimmer zoom optical systems having a higher zoom ratio in particular.
As one approach to a slimmer optical system, there is a technique wherein its optical path is bent substantially at right angles using a prism or mirror. As one approach to an optical system having a higher zoom ratio with a longer optical entire length, Patent Publications 1 and 2, referred to below, set forth an optical system wherein there is a second reflecting surface further located on an image plane side with respect to the first reflecting surface to achieve an additional bending of the optical axis.
Patent Publication 1
JP-A-2004-170707
Patent Publication 2
JP-A-2005-321452
With these prior arts with the optical axis bent twice, size reductions are still less than satisfactory because the entrance pupil position remains far on the wide-angle side, causing optical elements on the entrance side to grow large.